1. Field
One embodiment of the invention relates to a printed circuit board, an electronic device provided with the printed circuit board, and a manufacturing method for the printed circuit board, for example, a structure and a method for mounting a circuit component.
2. Description of the Related Art
An electronic device such as a portable computer includes a printed circuit board. The printed circuit board includes a printed wiring board and a circuit component mounted on the wiring board. A conductive pattern is formed on the wiring board. An IC chip or capacitor is an example of the circuit component.
In recent years, a surface mount system has been widely used as a method of mounting the circuit component on the printed wiring board. According to the surface mount system, bumps on the lower surface of the circuit component are bonded to pads on the surface of the printed wiring board. In general, each pad is formed of a smooth copper foil or the like. Therefore, each bonded surface of each pad and each bump is a flat surface that extends along the shape of the pad.
A printed wiring board having a recess in a conductive layer is described in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2003-303849. This printed wiring board includes a conductive layer formed having a recess and a spherical connecting member mounted therein. When a semiconductor element is mounted on the printed board, the connecting member is plastically deformed and partially gets into the recess. This connecting member connects the semiconductor element electrically to the printed wiring board.
If the bonded surfaces of the pad and the bump are flat surfaces, the bond area between them cannot be very large. Therefore, the bond strength, especially the shear strength, between the pad and the bump cannot be very high. If the bond strength between the pad and the bump is not high enough, the bonded surfaces of the pad and the bump may possibly be separated when the circuit component is subjected to a great force.